U.S. patent number 10,073,232 [Application Number 15/517,267] was granted by the patent office on 2018-09-11 for opto-electric hybrid board, and production method therefor.
This patent grant is currently assigned to NITTO DENKO CORPORATION. The grantee listed for this patent is NITTO DENKO CORPORATION. Invention is credited to Naoyuki Tanaka, Yuichi Tsujita.
United States Patent |
10,073,232 |
Tsujita , et al. |
September 11, 2018 |
Opto-electric hybrid board, and production method therefor
Abstract
An opto-electric hybrid board is provided, which includes an
electric circuit board including an electric wiring provided on a
front surface of an insulation layer, an optical waveguide provided
on a back side of the electric circuit board, and an outline
processing alignment mark positioned adjacent to an outline
processing portion on the front surface of the insulation layer on
the same basis as the electric wiring, and has an outline formed by
performing an outline processing operation with reference to the
outline processing alignment mark. The opto-electric hybrid board
has an accurate outline and, therefore, can be attached to other
component without an engagement failure or a connection
failure.
Inventors: |
Tsujita; Yuichi (Osaka,
JP), Tanaka; Naoyuki (Osaka, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
NITTO DENKO CORPORATION |
Ibaraki-shi, Osaka |
N/A |
JP |
|
|
Assignee: |
NITTO DENKO CORPORATION
(Ibaraki-shi, JP)
|
Family
ID: |
55760796 |
Appl.
No.: |
15/517,267 |
Filed: |
October 9, 2015 |
PCT
Filed: |
October 09, 2015 |
PCT No.: |
PCT/JP2015/078820 |
371(c)(1),(2),(4) Date: |
April 06, 2017 |
PCT
Pub. No.: |
WO2016/063752 |
PCT
Pub. Date: |
April 28, 2016 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20170307833 A1 |
Oct 26, 2017 |
|
Foreign Application Priority Data
|
|
|
|
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Oct 24, 2014 [JP] |
|
|
2014-217133 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05K
1/0269 (20130101); G02B 6/43 (20130101); H05K
1/0326 (20130101); H05K 1/0346 (20130101); G02B
6/122 (20130101); H05K 1/0274 (20130101); G02B
6/428 (20130101); H05K 3/18 (20130101); H05K
2201/0154 (20130101); G02B 6/138 (20130101); H05K
2203/166 (20130101); G02B 6/4214 (20130101); H05K
2201/10121 (20130101); H05K 2201/09918 (20130101); G02B
6/136 (20130101) |
Current International
Class: |
G02B
6/12 (20060101); H05K 3/18 (20060101); H05K
1/03 (20060101); G02B 6/122 (20060101); G02B
6/42 (20060101); H05K 1/02 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2004-294857 |
|
Oct 2004 |
|
JP |
|
2004294857 |
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Oct 2004 |
|
JP |
|
2007-241190 |
|
Sep 2007 |
|
JP |
|
2008-158221 |
|
Jul 2008 |
|
JP |
|
2009-31582 |
|
Feb 2009 |
|
JP |
|
2010-128200 |
|
Jun 2010 |
|
JP |
|
2012-155215 |
|
Aug 2012 |
|
JP |
|
2012-163649 |
|
Aug 2012 |
|
JP |
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2015-87475 |
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May 2015 |
|
JP |
|
Other References
International Search Report dated Dec. 28, 2015, issued in
counterpart International Application No. PCT/JP2015/078820 (2
pages). cited by applicant .
Notification of Transmittal of Copies of Translation of the
International Preliminary Report on Patentability (Form PCT/IB/338)
issued in counterpart International Application No.
PCT/JP2015/078820 dated May 4, 2017 with Forms PCT/IB/373 and
PCT/ISA/237. (11 pages). cited by applicant .
Office Action dated Jun. 19, 2018, issued in counterpart Japanese
Application No. 2014-217133, with English machine translation. (6
pages). cited by applicant.
|
Primary Examiner: Radkowski; Peter
Attorney, Agent or Firm: Westerman, Hattori, Daniels &
Adrian, LLP
Claims
What is claimed is:
1. An opto-electric hybrid board comprising: an electric circuit
board including an insulation layer and an electric wiring provided
on a front surface of the insulation layer; and an optical
waveguide provided on a side of the electric circuit board opposite
to the electric wiring, relative to the insulation layer having the
electric wiring provided on the front surface thereof; wherein a
portion of an end portion of the opto-electric hybrid board is an
outline processing surface; wherein an outline processing surface
forming alignment mark is positioned adjacent to the outline
processing surface on the front surface of the insulation layer on
a same basis as a basis for positioning the electric wiring
provided on the front surface of the insulation layer; and wherein
the opto-electric hybrid board has the outline processing surface
formed with reference to the outline processing surface forming
alignment mark.
2. The opto-electric hybrid board according to claim 1, wherein the
outline processing surface forming alignment mark is made of a same
material as the electric wiring.
3. The opto-electric hybrid board according to claim 1, wherein the
insulation layer is made of a polyimide resin.
4. An opto-electric hybrid board production method, comprising:
forming an electric wiring on a front surface of an insulation
layer to prepare an electric circuit board; forming an optical
waveguide on a side of the electric circuit board opposite to the
electric wiring, relative to the insulation layer having the
electric wiring provided on the front surface thereof, to fabricate
an opto-electric hybrid board; and performing an outline processing
operation on a portion of an end portion of the opto-electric
hybrid board to form an outline processing surface with reference
to an outline processing surface forming alignment mark; wherein
the electric circuit board preparing step includes forming the
outline processing surface forming alignment mark in adjacent
relation to an outline processing surface on the front surface of
the insulation layer, the outline processing surface forming
alignment mark being positioned on a same basis as a basis for
positioning the electric wiring on the front surface of the
insulation layer.
5. The opto-electric hybrid board production method according to
claim 4, wherein the outline processing surface forming alignment
mark is simultaneously formed from a same material as the electric
wiring, in adjacent relation to the outline processing surface,
when the electric wiring is formed on the front surface of the
insulation layer in the electric circuit board preparing step.
6. The opto-electric hybrid board production method according to
claim 4, wherein the insulation layer is made of a polyimide resin.
Description
TECHNICAL FIELD
The present disclosure relates to an opto-electric hybrid board
including an electric circuit board and an optical waveguide
stacked one on another, and a production method for the
opto-electric hybrid board.
BACKGROUND ART
To cope with increase in information transmission amount, recent
electronic devices and the like often employ opto-electric hybrid
boards which include electric wiring as well as optical wiring and
are capable of simultaneously transmitting electrical signals and
optical signals. As shown in FIG. 7, a known opto-electric hybrid
board includes, for example, an electric circuit board E including
an insulation layer 1 such as of a polyimide serving as a substrate
and an electric wiring 2 of an electrically conductive pattern
provided on a front surface of the insulation layer 1, and an
optical waveguide W provided on a back side of the electric circuit
board E and optically coupled to an optical element mounted at a
predetermined position on the electric wiring 2. A front surface of
the electric circuit board E is protected with a cover lay 3 for
insulation thereof. The optical waveguide W has a triple-layer
structure including an under-cladding layer 6, a core 7 serving as
an optical path, and an over-cladding layer 8.
The opto-electric hybrid board 10 may be mounted as it is in an
electronic device, or may include an opto-electric connection
ferrule attached to a distal end portion thereof for use as a
connector for connection between a plurality of boards or between
chips provided on a board.
Where a component such as the ferrule is attached to the
opto-electric hybrid board 10, it is important to accurately
position the component with respect to the opto-electric hybrid
board 10 so as to prevent an optical loss. Therefore, the core 7
serving as the optical path needs to be accurately positioned with
respect to the outline of the opto-electric hybrid board 10.
Accordingly, the outline of the opto-electric hybrid board 10,
particularly an end face of the opto-electric hybrid board 10 to be
connected to the component, should be processed with higher
dimensional accuracy.
Where the optical waveguide W per se is used as an optical
connector, the outline processing of the optical waveguide W
requires higher accuracy for the same reason as the outline
processing of the opto-electric hybrid board 10. To meet this
requirement, an optical waveguide production method for producing
the optical waveguide W is proposed, as shown in FIG. 8, which
includes the steps of forming an under-cladding layer 6,
simultaneously forming a core 7 and outline processing alignment
marks 11 from a core material on a surface (a lower surface in FIG.
8) of the under-cladding layer 6, and forming an over-cladding
layer 8 over the core 7 on the under-cladding layer 6 (on a lower
side in FIG. 8) with the alignment marks 11 uncovered (see PTL
1).
In the aforementioned production method, the core 7 serving as the
optical path and the alignment marks 11 are formed on the same
basis, so that the alignment marks 11 can be accurately positioned
with respect to the core 7. Further, the alignment marks 11 are
visible through the transparent under-cladding layer 6 as indicated
by arrows in FIG. 8. With reference to the alignment marks 11,
therefore, the outline processing operation can be advantageously
performed on the optical waveguide W with higher accuracy.
RELATED ART DOCUMENT
Patent Document
PTL 1: JP-A-2012-155215
SUMMARY OF INVENTION
It is contemplated to employ the aforementioned method involving
the simultaneous formation of the core 7 and the outline processing
alignment marks 11 for the opto-electric hybrid board production
method. However, the insulation layer 1 (see FIG. 7) of the
electric circuit board E of the opto-electric hybrid board 10 is
generally formed of a polyimide colored yellow or amber. Therefore,
the alignment marks 11 provided on the back side are less visible
through the colored insulation layer 1. This makes it difficult to
accurately perform the outline processing operation with reference
to the alignment marks 11.
In view of the foregoing, it is an object of the present invention
to provide an opto-electric hybrid board including an outline
processing alignment mark provided at an accurate position in a
readily visible manner and to provide a production method for the
opto-electric hybrid board.
According to a first inventive aspect to achieve the aforementioned
object, there is provided an opto-electric hybrid board which
includes: an electric circuit board including an insulation layer
and an electric wiring provided on a front surface of the
insulation layer; an optical waveguide provided on a side of the
electric circuit board opposite to the electric wiring, relative to
the insulation layer having the electric wiring provided on the
front surface thereof; and an outline processing alignment mark
positioned adjacent to an outline processing portion on the front
surface of the insulation layer on the same basis as a basis for
positioning the electric wiring provided on the front surface of
the insulation layer; the opto-electric hybrid board having an
outline formed with reference to the outline processing alignment
mark.
According to a second inventive aspect, the outline processing
alignment mark is made of the same material as the electric wiring
in the opto-electric hybrid board. According to a third inventive
aspect, the insulation layer is made of a polyimide resin in the
opto-electric hybrid board.
According to a fourth inventive aspect, there is provided an
opto-electric hybrid board production method, which includes the
steps of: forming an electric wiring on a front surface of an
insulation layer to prepare an electric circuit board; forming an
optical waveguide on a side of the electric circuit board opposite
to the electric wiring, relative to the insulation layer having the
electric wiring provided on the front surface thereof, to fabricate
an opto-electric hybrid board; and performing an outline processing
operation on the opto-electric hybrid board to impart the
opto-electric hybrid board with a predetermined outline; wherein
the electric circuit board preparing step includes the step of
forming an outline processing alignment mark in adjacent relation
to an outline processing portion on the front surface of the
insulation layer, the outline processing alignment mark being
positioned on the same basis as the basis for positioning the
electric wiring on the front surface of the insulation layer;
wherein the opto-electric hybrid board outline processing step
includes the step of performing the outline processing operation
with reference to the outline processing alignment mark.
According to a fifth inventive aspect, the outline processing
alignment mark is formed from the same material as the electric
wiring in adjacent relation to the outline processing portion when
the electric wiring is formed on the front surface of the
insulation layer in the electric circuit board preparing step of
the opto-electric hybrid board production method. According to a
sixth inventive aspect, the insulation layer is made of a polyimide
resin in the opto-electric hybrid board production method.
In the present disclosure, the term "outline processing operation"
means a processing operation employing a laser cutting process, a
grinding process, a machining process or other process for
imparting the opto-electric hybrid board with the predetermined
outline.
The inventors of the present invention conceived that the
visibility of the alignment mark can be enhanced by forming the
alignment mark on the front side rather than on the back side of
the colored insulation layer for improvement of the accuracy of the
outline processing operation to be performed on the opto-electric
hybrid board, and conducted intensive studies. As a result, the
inventors found that, where the alignment mark is not formed on the
back side of the insulation layer (board) simultaneously with the
core pattern but is formed on the front side of the insulation
layer on the same basis as the electric wiring pattern which is
accurately positioned for the positioning of the optical waveguide,
the alignment mark positioning accuracy is excellent and, in
addition, the alignment mark provided on the front side of the
insulation layer can be directly viewed and hence has excellent
visibility. Thus, the inventors attained the present invention.
The inventive opto-electric hybrid board is subjected to the
outline processing operation with reference to the highly visible
alignment mark positioned on the same basis as the electric wiring,
and the electric wiring is highly accurately positioned with
respect to the core pattern of the optical waveguide. Therefore,
the opto-electric hybrid board is imparted with an accurate outline
in highly accurate positional relation to the core pattern of the
optical waveguide by performing the outline processing operation
with reference to the alignment mark. Therefore, a ferrule or the
like can be properly engaged with the opto-electric hybrid board or
properly attached to a specific part of the opto-electric hybrid
board without an engagement failure, a connection failure or other
inconvenience.
The alignment mark is provided on the front side of the
opto-electric hybrid board in adjacent relation to the outline
processing portion, i.e., in adjacent relation to an end of the
board. Therefore, an additional processing operation or a product
quality inspecting operation can be advantageously performed with
reference to the alignment mark.
In the inventive opto-electric hybrid board, the outline processing
alignment mark is made of the same material as the electric wiring.
This makes it possible to simultaneously form the electric wiring
and the alignment mark, thereby further increasing the outline
processing accuracy. Therefore, this arrangement is
advantageous.
In the inventive opto-electric hybrid board, the insulation layer
is made of a polyimide resin. Even if the insulation layer is
colored yellow or amber, it is possible to perform the outline
processing operation while directly viewing the alignment mark
formed on the front surface of the insulation layer rather than
viewing the alignment mark through the colored insulation layer.
Therefore, this arrangement is particularly effective for practical
applications.
In the inventive opto-electric hybrid board production method, the
alignment mark can be accurately positioned on the front surface of
the insulation layer on the same basis as the electric wiring.
Therefore, the alignment mark can be disposed in accurate
positional relation to the core pattern of the optical waveguide
which is highly accurately positioned with respect to the electric
wiring. With reference to the alignment mark, the outline
processing operation can be performed on the opto-electric hybrid
board in highly accurate positional relation to the core pattern.
In addition, the alignment mark is disposed on the front side of
the opto-electric hybrid board. Therefore, the alignment mark can
be directly viewed by means of a camera or the like, so that the
processing operation can be performed with reference to a clear
image of the alignment mark.
In the inventive opto-electric hybrid board production method, the
outline processing alignment mark is formed from the same material
as the electric wiring in adjacent relation to the outline
processing portion on the front surface of the insulation layer
when the electric wiring is formed on the front surface of the
insulation layer in the electric circuit board preparing step. In
this case, the electric wiring and the alignment mark are formed on
a single common basis, so that the alignment mark can be accurately
positioned. Thus, the outline processing operation can be
advantageously performed with further higher accuracy. Without the
need for separately forming the alignment mark, this arrangement is
advantageous in terms of time and costs.
In the inventive opto-electric hybrid board production method, even
if the insulation layer of the opto-electric hybrid board is formed
of the polyimide resin to be thereby colored, the outline
processing alignment mark is visible. Therefore, the inventive
production method is more advantageous than the conventional
production method.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1A is a longitudinal sectional view schematically illustrating
an opto-electric hybrid board according to one embodiment of the
present invention, and FIG. 1B is a partial plan view of the
opto-electric hybrid board.
FIGS. 2A to 2D are diagrams for describing an electric circuit
board fabricating step in a method of producing the opto-electric
hybrid board.
FIGS. 3A to 3D are diagrams for describing an optical waveguide
fabricating step in the method of producing the opto-electric
hybrid board.
FIG. 4 is a diagram for describing an outline processing step in
the method of producing the opto-electric hybrid board.
FIG. 5 is a diagram for describing an outline processing step
according to another embodiment of the present invention.
FIGS. 6A to 6E are diagrams for describing variations of an
alignment mark to be employed in the present invention.
FIG. 7 is a diagram for describing a typical opto-electric hybrid
board.
FIG. 8 is a diagram for describing alignment marks provided in a
conventional optical waveguide.
DESCRIPTION OF EMBODIMENTS
Embodiments of the present invention will hereinafter be described
in detail based on the attached drawings. However, it should be
understood that the invention be not limited to these
embodiments.
FIG. 1A is a longitudinal sectional view schematically illustrating
an exemplary opto-electric hybrid board according to one embodiment
of the present invention, and FIG. 1B is a partial plan view of the
opto-electric hybrid board. The opto-electric hybrid board 10
includes an electric circuit board E including an insulation layer
1 and an electric wiring 2 provided on a front surface of the
insulation layer 1, and an optical waveguide W provided on a back
side of the insulation layer 1.
In the electric circuit board E, the electric wiring 2, which
includes optical element mounting pads 2a, a ground electrode 2b,
other element mounting pads and a connector mounting pad (not
shown), is provided on the front surface of the insulation layer 1
such as of a polyimide. An alignment mark 20 made of the same
material as the electric wiring 2 is provided on the front surface
of the insulation layer 1. As shown in FIG. 1B, the alignment mark
20 is positioned adjacent to one of longitudinal ends of the
opto-electric hybrid board 10, and is elongated transversely of the
opto-electric hybrid board.
The alignment mark 20 is used as a reference for defining a
processing position when an outline processing operation is
performed to impart the opto-electric hybrid board 10 with a
required predetermined outline in a production process for
producing the opto-electric hybrid board 10 as will be described
layer. A major feature of the present disclosure is that the
alignment mark 20 is provided on the front surface of the
insulation layer 1 as shown in FIG. 1B.
The electric wiring 2 excluding the pads 2a is protected with a
cover lay 3 such as of a polyimide for insulation. Surfaces of the
alignment mark 20 and the pads 2a uncovered with the cover lay 3
are each coated with an electroplating layer 4 such as of gold or
nickel.
On the other hand, the optical waveguide W provided on the back
side of the insulation layer 1 includes an under-cladding layer 6,
a core 7 provided in a predetermined pattern on a surface (a lower
surface in FIG. 1A) of the under-cladding layer 6, and an
over-cladding layer 8 unified with the surface of the
under-cladding layer 6 to cover the core 7. Reference numeral 9
designates a metal layer provided on a back surface of the
insulation layer 1 for reinforcing the opto-electric hybrid board
10. The metal layer 9 is configured in a certain pattern so as not
to cover a portion of the opto-electric hybrid board requiring
flexibility. The metal layer 9 has a through-hole 5 through which
an optical path extends between the core 7 and an optical element,
and the under-cladding layer 6 intrudes into the through-hole 5.
The metal layer 9 is optionally provided, and is not necessarily
required.
The core 7 has a surface inclined at 45 degrees with respect to a
core extending direction in association with the optical element
mounting pads 2a of the electric circuit board E. The inclined
surface serves as a light reflecting surface 7a which deflects
light transmitted through the core 7 by 90 degrees into a light
receiving portion of the light element or deflects light outputted
from a light emitting portion of the optical element by 90 degrees
into the core 7.
The opto-electric hybrid board 10 is produced, for example, in the
following manner by an inventive production method (see FIGS. 2A to
2D, FIGS. 3A to 3D and FIG. 4).
As shown in FIG. 2A, a planar metal layer 9 is first prepared.
Then, a photosensitive insulative resin such as containing a
polyimide is applied onto a surface of the metal layer 9, and
formed into an insulation layer 1 of a predetermined pattern by a
photography process. In this embodiment, a hole 1a through which
the surface of the metal layer 9 is partly exposed is formed in the
insulation layer 1 for formation of a ground electrode 2b (see FIG.
1A) in contact with the metal layer 9. The insulation layer 1 has a
thickness, for example, in a range of 3 to 50 .mu.m. Exemplary
materials for the metal layer 9 include stainless steel, copper,
silver, aluminum, nickel, chromium, titanium, platinum and gold,
among which stainless steel is preferred for rigidity. The
thickness of the metal layer 9 depends on the material for the
metal layer 9. Where stainless steel is used, the thickness of the
metal layer 9 is, for example, in a range of 10 to 70 .mu.m.
In turn, as shown in FIG. 2B, an electric wiring (including optical
element mounting pads 2a, the ground electrode 2b and other pads,
and this applies hereinafter) and an outline processing alignment
mark 20 are simultaneously formed, for example, by a semi-additive
method. In this method, a metal film (not shown) such as of copper
or chromium is first formed on a surface of the insulation layer 1
by sputtering or electroless plating. The metal layer serves as a
seed layer (a base layer for formation of an electroplating layer)
in the subsequent electroplating step. After a photosensitive
resist (not shown) is applied onto both surfaces of a stack
consisting of the metal layer 9, the insulation layer 1 and the
seed layer, holes for a pattern of the electric wiring 2 and holes
for the alignment mark 20 are formed in a photosensitive resist
layer present on the seed layer by a photolithography process.
Thus, surface portions of the seed layer are exposed in bottoms of
the holes. In turn, an electroplating layer such as of copper is
formed on the surface portions of the seed layer exposed in the
bottoms of the holes by electroplating. Then, the photosensitive
resist is lifted off with a sodium hydroxide aqueous solution.
Thereafter, a portion of the seed layer not formed with the
electroplating layer is removed by soft etching. Remaining portions
of a stack of the seed layer and the electroplating layer serve as
the electric wiring 2 and the alignment mark 20.
Subsequently, as shown in FIG. 2C, a photosensitive insulative
resin such as containing a polyimide is applied and patterned by a
photolithography process to form a cover lay 3 on a portion of the
electric wiring 2 other than the optical element mounting pads 2a
and the other pads.
In turn, as shown in FIG. 2D, an electroplating layer 4 is formed
on surfaces of the optical element mounting pads 2a, the other pads
and the alignment mark 20. Thus, an electric circuit board E is
fabricated.
A photosensitive resist is applied onto both surfaces of a stack of
the metal layer 9 and the electric circuit board E, and then holes
are formed in a photosensitive resist layer present on a back
surface of the metal layer 9 (opposite from the electrical circuit
board E) as corresponding to an unnecessary portion and a light
path through-hole formation portion of the metal layer 9 by a
photolithography process. Thus, back surface portions of the metal
layer 9 are exposed in the holes.
Then, the exposed portions of the metal layer 9 are removed by
etching with the use of an etching aqueous solution suitable for
the metal material for the metal layer 9 (with the use of a ferric
chloride aqueous solution, for example, where the metal layer 9 is
a stainless steel layer), whereby the insulation layer 1 is exposed
in the removed portions. Thereafter, the photosensitive resist is
lifted off with a sodium hydroxide aqueous solution or the like.
Thus, as shown in FIG. 3A, the metal layer 9 is formed only in a
region requiring reinforcement and, at the same time, an optical
path through-hole 5 is formed.
Subsequently, an optical waveguide W (see FIG. 1A) is fabricated on
the back surface of the insulation layer 1 (and on the back surface
of the metal layer 9). More specifically, as shown in FIG. 3B, a
photosensitive resin as a material for an under-cladding layer 6 is
first applied onto the back surfaces (lower surfaces in FIG. 3B) of
the insulation layer 1 and the metal layer 9, and then the
resulting layer is cured by exposure to radiation. Thus, the
under-cladding layer 6 is formed. At this time, the under-cladding
layer 6 may be patterned in a predetermined pattern by a
photolithography process. Thus, the under-cladding layer 6 is
configured so as to intrude into the optical path through-hole 5 of
the metal layer 9 to fill the through-hole 5. The under-cladding
layer 6 generally has a greater thickness than the metal layer 9
(as measured from the back surface of the insulation layer 1). When
a series of process steps for the fabrication of the optical
waveguide W are performed, the back surface of the insulation layer
1 formed with the metal layer 9 faces up. In FIGS. 3A to 3D,
however, the back surface of the insulation layer 1 is illustrated
as facing down.
Then, as shown in FIG. 3C, a core 7 is formed in a predetermined
pattern on a surface (a lower surface in FIG. 3C) of the
under-cladding layer 6 by a photolithography process. The core 7
has a thickness, for example, in a range of 3 to 100 .mu.m and a
width, for example, in a range of 3 to 100 .mu.m. An exemplary
material for the core 7 is the same type of photosensitive resin as
the under-cladding layer 6, but has a higher refractive index than
the materials for the under-cladding layer 6 and an over-cladding
layer 8 to be described later. The refractive index may be
controlled by selecting the types and the formulations of the
materials for the under-cladding layer 6, the core 7 and the
over-cladding layer 8.
Subsequently, as shown in FIG. 3D, the over-cladding layer 8 is
formed over a surface (a lower surface in FIG. 3D) of the
under-cladding layer 6 by a photolithography process to cover the
core 7. Thus, the optical waveguide W is fabricated. The
over-cladding layer 8 has a thickness that is greater than the
thickness of the core 7 and not greater than 300 .mu.m (as measured
from the surface of the under-cladding layer 6). An exemplary
material for the over-cladding layer 8 is the same type of
photosensitive resin as the under-cladding layer 6.
Specific examples of the formulations of the materials for the
optical waveguide W are as follows.
<Materials for Under-Cladding Layer 6 and Over-Cladding Layer
8>
20 parts by weight of an epoxy resin containing an alicyclic
skeleton (EHPE3150 available from Daicel Chemical Industries,
Ltd.)
80 parts by weight of a liquid long-chain bifunctional
semi-aliphatic epoxy resin (EXA-4816 available from DIC
Corporation)
2 parts by weight of a photoacid generator (SP170 available from
ADEKA Corporation)
40 parts by weight of ethyl lactate (available from Musashino
Chemical Laboratory, Ltd.)
<Material for Core 7>
50 parts by weight of o-cresol novolak glycidyl ether (YDCN-700-10
available from Nippon Steel & Sumikin Chemical Co., Ltd.)
50 parts by weight of bisphenoxyethanol fluorene diglycidyl ether
(OGSOL-EG available from Osaka Gas Chemicals Co, Ltd.)
1 part by weight of a photoacid generator (SP170 available from
ADEKA Corporation)
50 parts by weight of ethyl lactate (available from Musashino
Chemical Laboratory, Ltd.)
Then, a light reflecting surface 7a (see FIG. 1A) inclined at 45
degrees with respect to a core extending direction for optical
coupling to an optical element to be mounted on the front side of
the electric circuit board E is formed in a predetermined portion
of the optical waveguide W by laser processing, cutting or the
like. Then, the optical element is mounted on the pads 2a of the
electric wiring 2 provided on the front side of the electric
circuit board E, and other necessary components are mounted on the
board.
Thus, an opto-electric hybrid board 10 (yet to be subjected to an
outline processing operation) is provided. Then, as shown in FIG.
4, a cutting line is defined at a position spaced a predetermined
distance from the alignment mark 20 while the alignment mark 20 is
viewed by means of an alignment camera or the like, and the outline
processing operation is performed to cut the opto-electric hybrid
board 10 along the cutting line by laser (e.g., YAG laser). Thus,
the opto-electric hybrid board 10 is produced as having a
predetermined length with its core 7 exposed to one end face.
Instead of the laser, other cutting methods such as a dicing saw
may be used for the cutting of the opto-electric hybrid board
10.
The opto-electric hybrid board 10 thus produced (subjected to the
outline processing operation) has accurate outline dimensions as a
whole and is free from dimensional variations, because the end face
of the opto-electric hybrid board 10 is processed by performing the
cutting operation with higher dimensional accuracy with reference
to the alignment mark 20 which is formed adjacent to the
longitudinal end of the opto-electric hybrid board 10 on the same
basis as the electric wiring 2. Therefore, a ferrule or the like
can be advantageously engaged with the opto-electric hybrid board
10 or attached to a specific part of the opto-electric hybrid board
10 without an engagement failure, a connection failure or other
inconvenience. Further, an additional processing operation and a
product quality inspecting operation may be performed with
reference to the alignment mark 20.
In addition, the outline processing alignment mark 20
advantageously ensures proper finishing without any influence on a
laser processing operation or a dicing operation, because the
outline processing alignment mark 20 is not located on the outline
processing line (the cutting line in this embodiment) but located
in adjacent spaced relation to the processing line. More
specifically, if the alignment mark 20 made of the metal material
is provided on the processing line, irregularity is liable to occur
on a boundary between an alignment mark present portion and an
alignment mark absent portion of the opto-electric hybrid board
because of a difference in laser processing speed between the
alignment mark present portion and the alignment mark absent
portion in the laser processing operation. In the dicing operation,
irregularity is also liable to occur on the boundary because of a
difference in hardness between the alignment mark present portion
and the alignment mark absent portion. In a grinding operation,
metal powder of the alignment mark 20 consisting of metal material
generated by the grinding is liable to scratch the end face. If the
surface requiring higher processing accuracy has the irregularity
or the scratches, an optical loss may result. Therefore, where the
alignment mark 20 is not located on the processing line but located
in adjacent relation to the processing line as in the
aforementioned embodiment, it is possible to ensure excellent
finishing of the opto-electric hybrid board processed with higher
positional accuracy.
In the aforementioned embodiment, the opto-electric hybrid board 10
yet to be subjected to the outline processing operation has a
length slightly greater than a final length, and is cut at the end
portion thereof to the final length. Where an elongated sequence of
semi-finished opto-electric hybrid boards 10' produced by a
roll-to-roll process as shown in FIG. 5 is sequentially cut into
opto-electric hybrid boards 10 each having a predetermined length,
for example, cutting positions indicated by one-dot-and-dash lines
P are defined with reference to the alignment marks 20. While the
alignment marks 20 are sequentially recognized by means of an
alignment camera or the like, the semi-finished opto-electric
hybrid boards 10' are properly positioned to be cut. Thus, the
opto-electric hybrid boards 10 can be sequentially provided as each
having a proper length without variations.
In addition, where the opto-electric hybrid board 10 is to be
engaged with or attached to another component, the alignment mark
20 is effectively used as a dimensional reference for performing
the outline processing operation (the cutting operation, the
grinding operation or the like) to process the opto-electric hybrid
board 10 into a desired outline in conformity with the shape of the
component.
The plan shape of the alignment mark 20 is not limited to a single
elongated shape as shown in FIG. 1B. The alignment mark 20 may
include a plurality of alignment marks 20 disposed adjacent to a
cutting position indicated by a one-dot-and-dash line P as shown in
FIGS. 6A to 6D which illustrate variations of the alignment mark 20
having different configurations. As shown in FIG. 6E, a pair of
alignment marks 20 may be disposed on opposite sides of the cutting
position to form a cross-shaped void therebetween. Similarly, an
alignment mark 20 may be formed by covering a predetermined region
with the electric wiring material and forming a round void or a
polygonal void within the region. In any case, it is desired that
the alignment mark 20 is not located on the cutting position P but
is located in adjacent relation to the cutting position P for the
aforementioned reason.
In the aforementioned embodiment, the alignment mark 20 is
uncovered with the cover lay 3 for improvement of the visibility of
the alignment mark 20, and the surface of the alignment mark 20 is
covered with the electroplating layer 4 for protection thereof.
Where the alignment mark 20 is sufficiently visible through the
cover lay 3 depending on the color and the shape of the alignment
mark 20 and the transparency of the cover lay 3, the alignment mark
20 as well as the electric wiring 2 may be covered with the cover
lay 3.
In the opto-electric hybrid board 10, an alignment mark for
positioning the light reflecting surface 7a (see FIG. 1A) in the
core 7 and an alignment mark for positioning the optical element
may be simultaneously formed from the electric wiring material, or
a single alignment mark serving for these purposes may be formed
from the electric wiring material when the electric wiring 2 is
formed (see JP-2013-224450). Where these alignment marks and the
outline processing alignment mark 20 are simultaneously formed, the
formation of the electric wiring 2 and the formation of these
alignment marks can be achieved on a single common basis in a
single step. Thus, the opto-electric hybrid board 10 can be
advantageously produced as having a higher quality with the
electric wiring 2 and the alignment marks 20 being located in
highly accurate positional relation.
In the aforementioned embodiments, the outline processing alignment
mark 20 and the electric wiring 2 are simultaneously formed, but
are not necessarily required to be simultaneously formed. In some
case, the outline processing alignment mark 20 and the electric
wiring 2 may be separately formed on the same basis. However, the
simultaneous formation of the outline processing alignment mark 20
and the electric wiring 2 is preferred as in the aforementioned
embodiments, because their positional relationship is more
accurate.
While the specific embodiments of the present invention have been
shown, the embodiments are merely illustrative of the invention but
not limitative of the invention. It is contemplated that various
modifications apparent to those skilled in the art could be made
within the scope of the invention.
The present disclosure is employed to provide an opto-electric
hybrid board which has highly accurate outline dimensions, and is
stable in quality and free from any inconvenience when other
component is engaged with the opto-electric hybrid board or is
attached to a predetermined portion of the opto-electric hybrid
board.
REFERENCE SIGNS LIST
E: Electric circuit board W: Optical waveguide 1: Insulation layer
2: Electric wiring 10: Opto-electric hybrid board 20: Alignment
mark
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